Dielectric Layer for Touch Sensor Stack

ABSTRACT

In one embodiment, a touch sensor includes a substrate comprising a first surface. The touch sensor further includes a plurality of first electrodes comprising one or more conductive materials on the first surface. The touch sensor further includes a dielectric layer formed over the first electrodes and at least a portion of the first surface. The dielectric layer has a dielectric constant less than or equal to approximately 3.

TECHNICAL FIELD

This disclosure generally relates to touch sensors.

BACKGROUND

A touch sensor may detect the presence and location of a touch or theproximity of an object (such as a user's finger or a stylus) within atouch-sensitive area of the touch sensor overlaid on a display screen,for example. In a touch-sensitive-display application, the touch sensormay enable a user to interact directly with what is displayed on thescreen, rather than indirectly with a mouse or touch pad. A touch sensormay be attached to or provided as part of a desktop computer, laptopcomputer, tablet computer, personal digital assistant (PDA), smartphone,satellite navigation device, portable media player, portable gameconsole, kiosk computer, point-of-sale device, or other suitable device.A control panel on a household or other appliance may include a touchsensor.

There are a number of different types of touch sensors, such as (forexample) resistive touch screens, surface acoustic wave touch screens,and capacitive touch screens. Herein, reference to a touch sensor mayencompass a touch screen, and vice versa, where appropriate. When anobject touches or comes within proximity of the surface of thecapacitive touch screen, a change in capacitance may occur within thetouch screen at the location of the touch or proximity. A touch-sensorcontroller may process the change in capacitance to determine itsposition on the touch screen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example touch sensor with an example touch-sensorcontroller.

FIG. 2A illustrates an example dielectric layer formed on a bottomsurface of a substrate with conductive material forming electrodes.

FIG. 2B illustrates an example stack of a touch sensor that incorporatesthe dielectric layer of FIG. 2A.

FIG. 3 illustrates an example stack of a touch sensor that incorporatesthe dielectric layer of FIG. 2A, and further incorporates an exampledielectric layer formed on the top of a substrate.

FIG. 4 illustrates an example method for forming a stack of a touchsensor with a dielectric layer.

DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 illustrates an example touch sensor 10 with an exampletouch-sensor controller 12. Touch sensor 10 and touch-sensor controller12 may detect the presence and location of a touch or the proximity ofan object within a touch-sensitive area of touch sensor 10. Herein,reference to a touch sensor may encompass both the touch sensor and itstouch-sensor controller, where appropriate. Similarly, reference to atouch-sensor controller may encompass both the touch-sensor controllerand its touch sensor, where appropriate. Touch sensor 10 may include oneor more touch-sensitive areas, where appropriate. Touch sensor 10 mayinclude an array of drive and sense electrodes (or an array ofelectrodes of a single type) disposed on one or more substrates, whichmay be made of a dielectric material. Herein, reference to a touchsensor may encompass both the electrodes of the touch sensor and thesubstrate(s) that they are disposed on, where appropriate.Alternatively, where appropriate, reference to a touch sensor mayencompass the electrodes of the touch sensor, but not the substrate(s)that they are disposed on.

An electrode (whether a ground electrode, a guard electrode, a driveelectrode, or a sense electrode) may be an area of conductive materialforming a shape, such as for example a disc, square, rectangle, thinline, other suitable shape, or suitable combination of these. One ormore cuts in one or more layers of conductive material may (at least inpart) create the shape of an electrode, and the area of the shape may(at least in part) be bounded by those cuts. In particular embodiments,the conductive material of an electrode may occupy approximately 100% ofthe area of its shape. As an example and not by way of limitation, anelectrode may be made of indium tin oxide (ITO) and the ITO of theelectrode may occupy approximately 100% of the area of its shape(sometimes referred to as 100% fill), where appropriate. In particularembodiments, the conductive material of an electrode may occupysubstantially less than 100% of the area of its shape. As an example andnot by way of limitation, an electrode may be made of fine lines ofmetal or other conductive material (FLM), such as for example copper,silver, or a copper- or silver-based material, and the fine lines ofconductive material may occupy approximately 5% of the area of its shapein a hatched, mesh, or other suitable pattern. Herein, reference to FLMencompasses such material, where appropriate. Although this disclosuredescribes or illustrates particular electrodes made of particularconductive material forming particular shapes with particular fillpercentages having particular patterns, this disclosure contemplates anysuitable electrodes made of any suitable conductive material forming anysuitable shapes with any suitable fill percentages having any suitablepatterns.

Where appropriate, the shapes of the electrodes (or other elements) of atouch sensor may constitute in whole or in part one or moremacro-features of the touch sensor. One or more characteristics of theimplementation of those shapes (such as, for example, the conductivematerials, fills, or patterns within the shapes) may constitute in wholeor in part one or more micro-features of the touch sensor. One or moremacro-features of a touch sensor may determine one or morecharacteristics of its functionality, and one or more micro-features ofthe touch sensor may determine one or more optical features of the touchsensor, such as transmittance, refraction, or reflection.

A mechanical stack may contain the substrate (or multiple substrates)and the conductive material forming the drive or sense electrodes oftouch sensor 10. As an example and not by way of limitation, themechanical stack may include a first layer of optically clear adhesive(OCA) beneath a cover panel. The cover panel may be clear and made of aresilient material suitable for repeated touching, such as for exampleglass, polycarbonate, or poly(methyl methacrylate) (PMMA). Thisdisclosure contemplates any suitable cover panel made of any suitablematerial. The first layer of OCA may be disposed between the cover paneland the substrate with the conductive material forming the drive orsense electrodes. The mechanical stack may also include a second layerof OCA and a dielectric layer (which may be made of PET or anothersuitable material, similar to the substrate with the conductive materialforming the drive or sense electrodes). As an alternative, whereappropriate, a thin coating of a dielectric material may be appliedinstead of the second layer of OCA and the dielectric layer. The secondlayer of OCA may be disposed between the substrate with the conductivematerial making up the drive or sense electrodes and the dielectriclayer, and the dielectric layer may be disposed between the second layerof OCA and an air gap to a display of a device including touch sensor 10and touch-sensor controller 12. As an example only and not by way oflimitation, the cover panel may have a thickness of approximately 1 mm;the first layer of OCA may have a thickness of approximately 0.05 mm;the substrate with the conductive material forming the drive or senseelectrodes may have a thickness of approximately 0.05 mm; the secondlayer of OCA may have a thickness of approximately 0.05 mm; and thedielectric layer may have a thickness of approximately 0.05 mm. Althoughthis disclosure describes a particular mechanical stack with aparticular number of particular layers made of particular materials andhaving particular thicknesses, this disclosure contemplates any suitablemechanical stack with any suitable number of any suitable layers made ofany suitable materials and having any suitable thicknesses. As anexample and not by way of limitation, in particular embodiments, a layerof adhesive or dielectric may replace the dielectric layer, second layerof OCA, and air gap described above, with there being no air gap to thedisplay.

One or more portions of the substrate of touch sensor 10 may be made ofpolyethylene terephthalate (PET) or another suitable material. Thisdisclosure contemplates any suitable substrate with any suitableportions made of any suitable material. In particular embodiments, thedrive or sense electrodes in touch sensor 10 may be made of ITO in wholeor in part. In particular embodiments, the drive or sense electrodes intouch sensor 10 may be made of fine lines of metal or other conductivematerial. As an example and not by way of limitation, one or moreportions of the conductive material may be copper or copper-based andhave a thickness of approximately 5 μm or less and a width ofapproximately 10 μm or less. As another example, one or more portions ofthe conductive material may be silver or silver-based and similarly havea thickness of approximately 5 μm or less and a width of approximately10 μm or less. This disclosure contemplates any suitable electrodes madeof any suitable material.

Touch sensor 10 may implement a capacitive form of touch sensing. In amutual-capacitance implementation, touch sensor 10 may include an arrayof drive and sense electrodes forming an array of capacitive nodes. Adrive electrode and a sense electrode may form a capacitive node. Thedrive and sense electrodes forming the capacitive node may come neareach other, but not make electrical contact with each other. Instead,the drive and sense electrodes may be capacitively coupled to each otheracross a space between them. A pulsed or alternating voltage applied tothe drive electrode (by touch-sensor controller 12) may induce a chargeon the sense electrode, and the amount of charge induced may besusceptible to external influence (such as a touch or the proximity ofan object). When an object touches or comes within proximity of thecapacitive node, a change in capacitance may occur at the capacitivenode and touch-sensor controller 12 may measure the change incapacitance. By measuring changes in capacitance throughout the array,touch-sensor controller 12 may determine the position of the touch orproximity within the touch-sensitive area(s) of touch sensor 10.

In a self-capacitance implementation, touch sensor 10 may include anarray of electrodes of a single type that may each form a capacitivenode. When an object touches or comes within proximity of the capacitivenode, a change in self-capacitance may occur at the capacitive node andtouch-sensor controller 12 may measure the change in capacitance, forexample, as a change in the amount of charge needed to raise the voltageat the capacitive node by a pre-determined amount. As with amutual-capacitance implementation, by measuring changes in capacitancethroughout the array, touch-sensor controller 12 may determine theposition of the touch or proximity within the touch-sensitive area(s) oftouch sensor 10. This disclosure contemplates any suitable form ofcapacitive touch sensing, where appropriate.

In particular embodiments, one or more drive electrodes may togetherform a drive line running horizontally or vertically or in any suitableorientation. Similarly, one or more sense electrodes may together form asense line running horizontally or vertically or in any suitableorientation. In particular embodiments, drive lines may runsubstantially perpendicular to sense lines. Herein, reference to a driveline may encompass one or more drive electrodes making up the driveline, and vice versa, where appropriate. Similarly, reference to a senseline may encompass one or more sense electrodes making up the senseline, and vice versa, where appropriate.

Touch sensor 10 may have drive and sense electrodes disposed in apattern on one side of a single substrate. In such a configuration, apair of drive and sense electrodes capacitively coupled to each otheracross a space between them may form a capacitive node. For aself-capacitance implementation, electrodes of only a single type may bedisposed in a pattern on a single substrate. In addition or as analternative to having drive and sense electrodes disposed in a patternon one side of a single substrate, touch sensor 10 may have driveelectrodes disposed in a pattern on one side of a substrate and senseelectrodes disposed in a pattern on another side of the substrate.Moreover, touch sensor 10 may have drive electrodes disposed in apattern on one side of one substrate and sense electrodes disposed in apattern on one side of another substrate. In such configurations, anintersection of a drive electrode and a sense electrode may form acapacitive node. Such an intersection may be a location where the driveelectrode and the sense electrode “cross” or come nearest each other intheir respective planes. The drive and sense electrodes do not makeelectrical contact with each other—instead they are capacitively coupledto each other across a dielectric at the intersection. Although thisdisclosure describes particular configurations of particular electrodesforming particular nodes, this disclosure contemplates any suitableconfiguration of any suitable electrodes forming any suitable nodes.Moreover, this disclosure contemplates any suitable electrodes disposedon any suitable number of any suitable substrates in any suitablepatterns.

As described above, a change in capacitance at a capacitive node oftouch sensor 10 may indicate a touch or proximity input at the positionof the capacitive node. Touch-sensor controller 12 may detect andprocess the change in capacitance to determine the presence and locationof the touch or proximity input. Touch-sensor controller 12 may thencommunicate information about the touch or proximity input to one ormore other components (such one or more central processing units (CPUs))of a device that includes touch sensor 10 and touch-sensor controller12, which may respond to the touch or proximity input by initiating afunction of the device (or an application running on the device).Although this disclosure describes a particular touch-sensor controllerhaving particular functionality with respect to a particular device anda particular touch sensor, this disclosure contemplates any suitabletouch-sensor controller having any suitable functionality with respectto any suitable device and any suitable touch sensor.

Touch-sensor controller 12 may be one or more integrated circuits (ICs),such as for example general-purpose microprocessors, microcontrollers,programmable logic devices or arrays, application-specific ICs (ASICs).In particular embodiments, touch-sensor controller 12 comprises analogcircuitry, digital logic, and digital non-volatile memory. In particularembodiments, touch-sensor controller 12 is disposed on a flexibleprinted circuit (FPC) bonded to the substrate of touch sensor 10, asdescribed below. The FPC may be active or passive, where appropriate. Inparticular embodiments, multiple touch-sensor controllers 12 aredisposed on the FPC. Touch-sensor controller 12 may include a processorunit, a drive unit, a sense unit, and a storage unit. The drive unit maysupply drive signals to the drive electrodes of touch sensor 10. Thesense unit may sense charge at the capacitive nodes of touch sensor 10and provide measurement signals to the processor unit representingcapacitances at the capacitive nodes. The processor unit may control thesupply of drive signals to the drive electrodes by the drive unit andprocess measurement signals from the sense unit to detect and processthe presence and location of a touch or proximity input within thetouch-sensitive area(s) of touch sensor 10. The processor unit may alsotrack changes in the position of a touch or proximity input within thetouch-sensitive area(s) of touch sensor 10. The storage unit may storeprogramming for execution by the processor unit, including programmingfor controlling the drive unit to supply drive signals to the driveelectrodes, programming for processing measurement signals from thesense unit, and other suitable programming, where appropriate. Althoughthis disclosure describes a particular touch-sensor controller having aparticular implementation with particular components, this disclosurecontemplates any suitable touch-sensor controller having any suitableimplementation with any suitable components.

Tracks 14 of conductive material disposed on the substrate of touchsensor 10 may couple the drive or sense electrodes of touch sensor 10 toconnection pads 16, also disposed on the substrate of touch sensor 10.As described below, connection pads 16 facilitate coupling of tracks 14to touch-sensor controller 12. Tracks 14 may extend into or around (e.g.at the edges of) the touch-sensitive area(s) of touch sensor 10.Particular tracks 14 may provide drive connections for couplingtouch-sensor controller 12 to drive electrodes of touch sensor 10,through which the drive unit of touch-sensor controller 12 may supplydrive signals to the drive electrodes. Other tracks 14 may provide senseconnections for coupling touch-sensor controller 12 to sense electrodesof touch sensor 10, through which the sense unit of touch-sensorcontroller 12 may sense charge at the capacitive nodes of touch sensor10. Tracks 14 may be made of fine lines of metal or other conductivematerial. As an example and not by way of limitation, the conductivematerial of tracks 14 may be copper or copper-based and have a width ofapproximately 100 μm or less. As another example, the conductivematerial of tracks 14 may be silver or silver-based and have a width ofapproximately 100 μm or less. In particular embodiments, tracks 14 maybe made of ITO in whole or in part in addition or as an alternative tofine lines of metal or other conductive material. Although thisdisclosure describes particular tracks made of particular materials withparticular widths, this disclosure contemplates any suitable tracks madeof any suitable materials with any suitable widths. In addition totracks 14, touch sensor 10 may include one or more ground linesterminating at a ground connector (which may be a connection pad 16) atan edge of the substrate of touch sensor 10 (similar to tracks 14).

Connection pads 16 may be located along one or more edges of thesubstrate, outside the touch-sensitive area(s) of touch sensor 10. Asdescribed above, touch-sensor controller 12 may be on an FPC. Connectionpads 16 may be made of the same material as tracks 14 and may be bondedto the FPC using an anisotropic conductive film (ACF). Connection 18 mayinclude conductive lines on the FPC coupling touch-sensor controller 12to connection pads 16, in turn coupling touch-sensor controller 12 totracks 14 and to the drive or sense electrodes of touch sensor 10. Inanother embodiment, connection pads 16 may be connected to anelectro-mechanical connector (such as a zero insertion forcewire-to-board connector); in this embodiment, connection 18 may not needto include an FPC. This disclosure contemplates any suitable connection18 between touch-sensor controller 12 and touch sensor 10.

Particular embodiments of the present disclosure include a dielectriclayer providing a protective coating over conductive material formed ona substrate of a stack of a touch sensor 10. The dielectric layer has alow dielectric constant, such as, for example, less than or equal toapproximately 3. Further examples of the low dielectric constant of thedielectric layer are discussed in detail below. The dielectric layer maybe formed by applying a thin coating of a dielectric material over thesubstrate and conductive material before they are integrated with theother components of the stack. As an example and not by way oflimitation, a dielectric layer may be placed on a bottom surface of asubstrate and the conductive material formed on the substrate.

In particular embodiments, the dielectric layer may attenuate noise(such as electro magnetic radiation) generated by an electronic displaypanel. An electronic display unit typically generates noise that mayhave a negative effect on the touch sensor. The dielectric layer mayattenuate the noise (or a portion of the noise) generated by theelectronic display unit, thereby improving the performance of the touchsensor. In particular embodiments, the dielectric layer may also protectthe conductive material on the substrate during manufacturing of thetouch sensor and thereafter. For example and not by way of limitation,the dielectric layer may protect the conductive material from corrosion(e.g. rust) and/or abrasions. In particular embodiments, the dielectriclayer may further keep the conductive lines in place on the substrate.

In traditional systems, a layer of optically clear adhesive and aprotective shield layer (such as an ITO shield layer, a PDot(Poly(3,4-ethylenedioxythiophene)) shield layer, a carbon nano tubeshield layer, or any other clear conductive layer connected to ground)are laminated to the substrate and conductive material formed thereon.This protective shield layer may act as a shield against noise generatedby the electronic display unit when connected to ground. While adding aprotective shield layer in-between the sensor substrate (such as thesubstrate and conductive material forming the drive or sense electrodesof a touch sensor) and the electronic display unit may attenuate noisegenerated by the electronic display unit and/or protect the conductivematerial formed on the sensor substrate, such a method involves extraprocessing steps (such as alignment of the protective shield layer withthe substrate and connecting the protective shield layer to ground) andmaterials that are not necessary if a dielectric layer is used instead.Furthermore, a protective shield layer may be expensive. Additionally,the protective shield layer may also create a ground loading effectwhich tends to attract electric fields of the touch sensor to the groundlayer, thereby decreasing the sensitivity of the touch sensor.

In other traditional systems, in order to attenuate noise generated byan overly noisy electronic display unit, the touch sensor may utilize anair gap in-between the sensor substrate and the electronic display unit(or in-between the protective shield layer and the electronic displayunit). The use of such an air gap, however, may decrease transmissivityof light from the electronic display unit because of the largedifference between the refractive index of the air and the refractiveindex of the sensor substrate (or the protective shield layer). Inparticular embodiments, the dielectric layer having a low dielectricconstant may provide better attenuation of the noise from the electronicdisplay unit, thereby allowing the touch sensor to be created without anair gap in-between the dielectric layer and the electronic display unit.

FIG. 2A illustrates an example dielectric layer 20 formed on a bottomsurface of a substrate 22 with conductive material forming electrodes24. As depicted, dielectric layer 20 is formed over sense electrodes 24b. The dielectric layer 20 on the bottom surface of substrate 22 mayoverlay and protect any other suitable conductive elements of touchsensor 10, such as sense lines, drive lines, tracks 14, or connectionpads 16. In the embodiment depicted, dielectric layer 20 has a lowdielectric constant.

In particular embodiments, a low dielectric constant refers to adielectric constant that is less than or equal to approximately 3. Thedielectric layer 20 may have any dielectric constant that is less thanor equal to approximately 3. As examples and not by way of limitation,the dielectric layer may have a dielectric constant that is equal to 3,2.8, 2.7, 2.5, 2.25, 2, 1.75, 1.5, 1.25, 1.1, 1, and/or any otherdielectric constant that is less than or equal to approximately 3. Inparticular embodiments, a low dielectric constant may include any othersuitable range of low dielectric constants. As examples and not by wayof limitation, a low dielectric constant may include any dielectricconstant that is less than or equal to approximately 3 and greater than1, less than approximately 3 and greater than approximately 2, less thanapproximately 3 and greater than approximately 2.5, less thanapproximately 3 and greater than approximately 2.75, less thanapproximately 3 and greater than approximately 2.85, less thanapproximately 2 and greater than approximately 1, less than 3 andgreater than approximately 2, less than 3 and greater than approximately2.5, less than 3 and greater than approximately 2.85, or any othersuitable range of low dielectric constants. Furthermore, the term“approximately” may refer to minor variations in a dielectric constant.For example and not by way of limitation, “approximately” may refer tovariations of the dielectric constant of 0.1 or less. Such variationsmay be the result of the manufacturing process of the dielectric layer20.

The dielectric layer 20 may be formed of any suitable material with alow dielectric constant. Furthermore, the dielectric layer 20 may beformed by lowering the dielectric constant of any suitable materialtype. As an example and not by way of limitation, a material type (suchas varnish, shellac, lacquer, PMMA, polycarbonate, or other polymer) maybe doped with other compounds in order to lower the dielectric constantof the material type, as would be understood by one of ordinary skill inthe art based on the present disclosure.

In the embodiment depicted, dielectric layer 20 forms a substantiallyflat sheet over substrate 22. That is, the bottom surface of dielectriclayer 20 maintains a uniform thickness with respect to the bottomsurface of substrate 22. Such embodiments may allow a dielectric layer20 to interface with other flat elements of a touch sensor stack, suchas an electronic display panel. In another embodiment, dielectric layer20 generally conforms with the shape of substrate 22 and the conductivematerial formed thereon. For example and not by way of limitation, aportion of the dielectric layer 20 that contacts the bottom surface ofsubstrate 22 may rest higher than another portion of the dielectriclayer that overlays a sense electrode 24 b that is raised from thesurface of the substrate. In such embodiments, each point of thedielectric layer 20 may have a generally constant thickness whenmeasured from the element (e.g. substrate 22 or sense electrode 24 b)contacted by the dielectric layer at that point.

The dielectric layer 20 is formed by applying a thin coating of adielectric material over the substrate 22 and conductive material formedthereon. In particular embodiments, there is no adhesive layer betweenthe dielectric layer 20 and substrate 22 and/or conductive materialformed thereon. The dielectric layer 20 may have any suitable thickness,such as between about 0.5 and about 50 microns. In various embodiments,the dielectric layer 20 is less than 10 microns. In a particularembodiment, the dielectric layer 20 is between about 0.5 and about 4microns. The dielectric layer 20 may include any suitable physicalcharacteristics, such as good adhesion (to substrate 22 and anelectronic display unit), durability, and suitable optical properties(e.g. the material should be clear so that the electronic display panelcan be viewed through the dielectric layer 20).

The dielectric material may be formed on the substrate 22 and conductivematerial in any suitable manner. In a particular embodiment, aroll-to-roll process is used to apply the dielectric material tosubstrate 22 and the conductive material formed thereon. In such anembodiment, a roll may include a plurality of segments that each includea discrete substrate 22 and conductive material. Another roll mayinclude a thin film of dielectric material. The dielectric material fromthis roll may be laminated or otherwise applied to the segments of thefirst roll, resulting in the formation of dielectric layers 20 onsubstrates 22 and the conductive materials formed thereon. In variousembodiments, when the dielectric layer 20 is formed on substrate 22using such a lamination method, dielectric layer 20 has a thickness ofabout 50 microns.

In some embodiments, the dielectric material is applied in a liquid (orsemi-liquid or other malleable) form and allowed to cure (such as athermal cure or an ultraviolet cure) into a hard protective coating oversubstrate 22 and the conductive material. Any suitable method may beused to apply the dielectric material to the substrate 22. For exampleand not by way of limitation, the dielectric material may be screenprinted on the substrate 22 and the conductive material. As anotherexample and not by way of limitation, a roller or brush may be used tocoat the dielectric material on the substrate 22 and conductivematerial. As another example and not by way of limitation, the substrate22 and conductive material may be immersed in and then removed from apool of the dielectric material. As yet other examples and not by way oflimitation, the dielectric material may be sprayed, poured, or inkjetprinted onto substrate 22 and the conductive material. In various suchembodiments, dielectric layer 20 has a thickness between about 2 micronsand about 50 microns.

The dielectric layer 20 may be formed at any suitable time duringmanufacturing of touch sensor 10. For example and not by way oflimitation, the dielectric layer 20 may be formed immediately or soonafter the conductive material is formed on substrate 22. In particularembodiments, a series of substrates may be processed in succession.Conductive material is formed on one substrate, a dielectric layer isthen formed on that substrate, conductive material is formed on the nextsubstrate, a dielectric layer is formed on that substrate, and so on.Such a method may be relatively fast and inexpensive compared to othersolutions where a layer of adhesive and other component (such as aprotective carrier or dielectric layer) has to be aligned with andapplied to the substrate. Once the dielectric layer 20 is formed, itprotects against corrosion (e.g. rust) of the conductive material thatcan occur if the substrate and conductive material is exposed tomoisture or other corrosion facilitating material.

FIG. 2B illustrates an example stack 34 of touch sensor 10 thatincorporates the dielectric layer 20 of FIG. 2A. Stack 34 includeselectrodes 24 formed on substrate 22, a cover panel 26 coupled tosubstrate 22 via a layer of adhesive 28, and dielectric layer 20 appliedto the bottom surface of substrate 22 and conductive material formedthereon. In particular embodiments, there is no adhesive layer betweenthe dielectric layer 20 and substrate 22 and/or electrodes 24 formedthereon. The dielectric layer 20 is configured to interface withelectronic display panel 32. For example and not by way of limitation,as depicted, the dielectric layer 20 may face electronic display panel32 with an air gap 31 between dielectric layer 20 and electronic displaypanel 32. In such embodiments, the dielectric layer may be sufficientlythick (e.g. greater than or equal to about 2 microns) and smooth suchthat visual interference effects (such as rainbow effects) are avoidedor mitigated. As another example and not by way of limitation, thedielectric layer 20 may be in direct contact with electronic displaypanel 32 (such as when the dielectric layer 20 is a liquid opticallyclear adhesive (LOCA), a low dielectric constant OCA, or any othersuitable adhesive). In such an example, there is no air gap in-betweenthe dielectric layer 20 and the electronic display panel 32. Electronicdisplay panel 32 may be a liquid crystal display (LCD), light emittingdiode (LED) display, or other suitable electronic display.

FIG. 3 illustrates an example stack 36 of a touch sensor thatincorporates the dielectric layer of FIG. 2A, and further incorporatesan example dielectric layer formed on the top of a substrate. Stack 36includes electrodes 24 formed on substrate 22, dielectric layers 20 and33 formed on the bottom and top surfaces of substrate 22 and theelectrodes 24, and a cover panel 26 formed over dielectric layer 33.

The dielectric layer 20 of FIG. 3 may have any of the characteristicsdescribed above in connection with the dielectric layer 20 of FIGS. 2Aand 2B. Furthermore, the dielectric layer 20 may be formed of any of thematerials described above in connection with the dielectric layer 20 ofFIGS. 2A and 2B, and further may be formed by any of the methodsdescribed above in connection with the dielectric layer 20 of FIGS. 2Aand 2B. The dielectric layer 20 is configured to interface withelectronic display panel 32. For example and not by way of limitation,as depicted, the dielectric layer 20 may face electronic display panel32 with an air gap 31 between dielectric layer 20 and electronic displaypanel 32. As another example and not by way of limitation, thedielectric layer 20 may be in direct contact with electronic displaypanel 32 (as is discussed above). In such an example, there is no airgap in-between the dielectric layer 20 and the electronic display panel32. As a further example, the dielectric layer 20 may be in indirectcontact with electronic display panel 32 (such as when an OCA connectsdielectric layer 20 to electronic display panel 32).

As depicted, dielectric layer 33 is formed over drive electrodes 24 a.In particular embodiments, there is no adhesive layer between thedielectric layer 33 and substrate 22 and/or drive electrodes 24 a formedthereon. The dielectric layer 33 may also overlay and protect any othersuitable conductive elements of touch sensor 10, such as senseelectrodes 24 b, drive lines, sense lines, tracks 14, or connection pads16. In particular embodiments, because dielectric layer 33 is formed onthe top side of substrate 22, dielectric layer 33 may have a higherdielectric constant than dielectric layer 20. As an example and not byway of limitation, although dielectric layer 20 may have a dielectricconstant that is less than or equal to approximately 3, dielectric layer33 may have a dielectric constant that is greater than 3. In particular,the dielectric layer 33 may have a dielectric constant that is less thanor equal to approximately 4 and greater than 3. In particularembodiments, the higher dielectric constant of dielectric layer 33 mayprevent dielectric layer 33 from adversely affecting touch sensor 10. Inparticular embodiments, dielectric layer 33 may only overlay and protecttracks 14 on the top side of substrate 22. In such embodiments,dielectric layer 33 may have a dielectric constant that is less than orequal to approximately 3.

The dielectric layer 33 may be formed of any suitable material. Examplesof suitable materials for forming dielectric layer 33 include varnish,shellac, lacquer, PMMA, or polycarbonate. In particular embodiments, thedielectric material may be chosen to index match the material of thecover panel. This may include choosing a dielectric material withoptical properties that are similar to optical properties of the coverpanel in order to minimize visual distortions (such as rainbow effects)that can arise from dissimilarities between the cover panel and thedielectric layer 33. In one embodiment, index matching is achieved byforming a dielectric layer 33 made of the same material as the coverpanel. For example and not by way of limitation, the dielectric layer 33may be made of PMMA and the cover panel formed by injecting PMMA resinduring an in-mold lamination (IML) process.

The dielectric layer 33 may be formed in any suitable manner, such asthat described above in connection with dielectric layer 20. Inparticular embodiments, dielectric 33 may be formed using a process thatis different from a process used to form dielectric layer 20. As anexample and not by way of limitation, dielectric layer 33 may be formedby a roll-to-roll process and dielectric layer 20 may be formed by ascreen printing process. In other embodiments, dielectric layers 20 anddielectric layer 33 may be formed using the same process.

In particular embodiments, the dielectric layer 33 may include any ofthe physical characteristics described above in connection withdielectric layer 20. For example and not by way of limitation, thedielectric layer 33 may include good adhesion (to substrate 22),durability, and suitable optical properties (e.g. the material should beclear so that the electronic display panel can be viewed through thedielectric layer 33). As another example and not by way of limitation,dielectric layer 33 may form a substantially flat sheet over thesubstrate 22 or may generally conform with the shape of the substrate 33and conductive material formed thereon (such as drive electrodes 24 a).

Although example stack configurations have been shown, dielectric layer33 may be applied within a stack of a touch sensor 10 in any suitablemanner. As examples and not by way of limitation, dielectric layer 33may be applied to the top surface of multiple substrates, to the bottomsurface of multiple substrates, or both.

In particular embodiments, the dielectric layer (such as dielectriclayer 20 and/or dielectric layer 33) is applied to only a portion of asurface of substrate 22. As an example and not by way of limitation, thedielectric layer may be omitted from the area of the substrate 22 onwhich the connection pads 16 are formed, so as not to interfere withcoupling between controller 12 and the connection pads. In otherembodiments, the dielectric layer is applied to the portion of substrate22 that includes the connection pads 16, but portions of the dielectriclayer are subsequently removed from the connection pads 16 in order toexpose at least a portion of the connection pads 16. Portions of thedielectric layer may be removed in any suitable manner, such as throughapplication of a solvent. In yet other embodiments, the dielectric layermay be applied to the portion of substrate 22 that includes theconnection pads 16, but the dielectric layer is sufficiently thin (e.g.about 0.5-4 microns) to allow ACF to penetrate through the dielectriclayer 20 during bonding between the connection pads 16 and an FPC.

FIG. 4 illustrates an example method for forming a stack of a touchsensor 10 with a dielectric layer 20. The method begins as substrate 22is formed at step 50. Substrate 22 may be formed in any suitable mannerand, as discussed earlier, may comprise PET. At step 52, conductivematerial is formed on substrate 22. The conductive material may beformed on any suitable surface of the substrate 22. Any suitableconductive elements may be formed from the conductive material, such astracks 14, connection pads 16, drive electrodes 24 a, sense electrodes24 b, drive lines, or sense lines. The conductive elements may be madeof any suitable material such as FLM, ITO, or carbon nanotubes.

At step 54, a dielectric layer 20 is applied to the substrate 22 withthe conductive material. The dielectric layer 20 has a low dielectricconstant. In particular embodiments, the dielectric layer 20 may haveany dielectric constant that is less than or equal to approximately 3,such as a dielectric constant that is equal to 3, 2.8, 2.7, 2.5, 2.25,2, 1.75, 1.5, 1.25, 1.1, 1, and/or any other dielectric constant that isless than or equal to approximately 3. The dielectric layer 20 may beformed over any suitable portion or all of one or more surfaces of thesubstrate 22.

At step 56, the substrate 22 is cut to the desired size. The substratemay be cut in any suitable manner. At step 58, an electronic displaypanel 32 is attached to the substrate 22. The electronic display panel32 may be attached in any suitable manner. In particular embodiments,the electronic display panel 32 may be attached to the substrate 22 suchthat the dielectric layer 20 may face electronic display panel 32 withan air gap 31 between dielectric layer 20 and electronic display panel32. In particular embodiments, the electronic display panel 32 may beattached to the substrate 22 such that the dielectric layer 20 may be indirect contact with the electronic display panel 32. In suchembodiments, there is no air gap in-between the dielectric layer 20 andthe electronic display panel 32. In particular embodiments, theelectronic display panel 32 may be attached to the substrate 22 suchthat the dielectric layer 20 may be in indirect contact with theelectronic display panel 32 (such as when an OCA connects the dielectriclayer 20 to the electronic display panel 32).

At step 60, cover panel 26 is applied to the substrate 22 or anothersubstrate in the stack. In particular embodiments, a separatelymanufactured cover panel 26 is applied to the top surface of thesubstrate via an adhesive layer 28 or dielectric layer 33. In otherembodiments, the cut substrate 22 is presented to an IML tool and thecover panel 26 is formed over a dielectric layer 33 on the top surfaceof the substrate.

Particular embodiments may repeat the steps of the method of FIG. 4,where appropriate. Moreover, although this disclosure describes andillustrates particular steps of the method of FIG. 4 as occurring in aparticular order, this disclosure contemplates any suitable steps of themethod of FIG. 4 occurring in any suitable order. Furthermore, althoughthis disclosure describes and illustrates particular components,devices, or systems carrying out particular steps of the method of FIG.4, this disclosure contemplates any suitable combination of any suitablecomponents, devices, or systems carrying out any suitable steps of themethod of FIG. 4.

Although FIGS. 1-4 have been described above as including particularcomponents and/or steps, the systems and methods of FIGS. 1-4 mayinclude any combination of any of the described components and any ofthe options, features, or steps described herein, as would be understoodby one of ordinary skill in the art based upon the teachings of thedisclosure. For example and not by way of limitation, any of theoptions, features, or steps described herein may be utilized incombination with the illustrated embodiments of FIGS. 1-4 and/or anynumber of the other options, features, or steps also described herein aswould be understood by one of ordinary skill in the art based upon theteachings of the disclosure.

Herein, reference to a computer-readable non-transitory storage mediumor media may include one or more semiconductor-based or other integratedcircuits (ICs) (such, as for example, a field-programmable gate array(FPGA) or an application-specific IC (ASIC)), hard disk drives (HDDs),hybrid hard drives (HHDs), optical discs, optical disc drives (ODDs),magneto-optical discs, magneto-optical drives, floppy diskettes, floppydisk drives (FDDs), magnetic tapes, solid-state drives (SSDs),RAM-drives, SECURE DIGITAL cards, SECURE DIGITAL drives, any othersuitable computer-readable non-transitory storage medium or media, orany suitable combination of two or more of these, where appropriate. Acomputer-readable non-transitory storage medium or media may bevolatile, non-volatile, or a combination of volatile and non-volatile,where appropriate.

Herein, “or” is inclusive and not exclusive, unless expressly indicatedotherwise or indicated otherwise by context. Therefore, herein, “A or B”means “A, B, or both,” unless expressly indicated otherwise or indicatedotherwise by context. Moreover, “and” is both joint and several, unlessexpressly indicated otherwise or indicated otherwise by context.Therefore, herein, “A and B” means “A and B, jointly or severally,”unless expressly indicated otherwise or indicated otherwise by context.

This disclosure encompasses all changes, substitutions, variations,alterations, and modifications to the example embodiments herein that aperson having ordinary skill in the art would comprehend. Moreover,reference in the appended claims to an apparatus or system or acomponent of an apparatus or system being adapted to, arranged to,capable of, configured to, enabled to, operable to, or operative toperform a particular function encompasses that apparatus, system,component, whether or not it or that particular function is activated,turned on, or unlocked, as long as that apparatus, system, or componentis so adapted, arranged, capable, configured, enabled, operable, oroperative.

What is claimed is:
 1. A touch sensor comprising: a substrate comprisinga first surface; a plurality of first electrodes comprising one or moreconductive materials on the first surface; and a dielectric layer formedover the first electrodes and at least a portion of the first surface,the dielectric layer having a dielectric constant less than or equal toapproximately
 3. 2. The touch sensor of claim 1, wherein the dielectriclayer is configured to face an electronic display panel with an air gapbetween the dielectric layer and the electronic display panel.
 3. Thetouch sensor of claim 1, wherein the dielectric layer is in at leastindirect contact with an electronic display panel.
 4. The touch sensorof claim 1, wherein there is no adhesive layer between the dielectriclayer and the first electrodes.
 5. The touch sensor of claim 1, furthercomprising: a plurality of second electrodes comprising one or moreconductive materials on a second surface of the first substrate or asecond substrate; a second dielectric layer formed on the secondelectrodes and at least a portion of the second surface; and asubstantially transparent cover panel disposed on the dielectric layer.6. The touch sensor of claim 1, wherein the conductive materialscomprise indium tin oxide, a plurality of fine lines of metal, or aplurality of carbon nanotubes.
 7. The touch sensor of claim 1, whereinthe dielectric constant of the dielectric layer is less thanapproximately 2 and greater than approximately 1
 8. The touch sensor ofclaim 1, wherein the dielectric constant of the dielectric layer is lessthan approximately 3 and greater than approximately
 2. 9. A devicecomprising: a touch sensor comprising: a substrate comprising a firstsurface; a plurality of first electrodes comprising one or moreconductive materials on the first surface; and a dielectric layer formedover the first electrodes and at least a portion of the first surface,the dielectric layer having a dielectric constant less than or equal toapproximately 3; and one or more computer-readable non-transitorystorage media coupled to the touch sensor and embodying logic that isconfigured when executed to control the touch sensor.
 10. The device ofclaim 9, wherein the dielectric layer is configured to face anelectronic display panel with an air gap between the dielectric layerand the electronic display panel.
 11. The device of claim 9, wherein thedielectric layer is in at least indirect contact with an electronicdisplay panel.
 12. The device of claim 9, wherein there is no adhesivelayer between the dielectric layer and the first electrodes.
 13. Thedevice of claim 9, wherein the touch sensor further comprises: aplurality of second electrodes comprising one or more conductivematerials on a second surface of the first substrate or a secondsubstrate; a second dielectric layer formed on the second electrodes andat least a portion of the second surface; and a substantiallytransparent cover panel disposed on the dielectric layer.
 14. The deviceof claim 9, wherein the conductive materials comprise indium tin oxide,a plurality of fine lines of metal, or a plurality of carbon nanotubes.15. The device of claim 9, wherein the dielectric constant of thedielectric layer is less than approximately 2 and greater thanapproximately
 1. 16. The device of claim 9, wherein the dielectricconstant of the dielectric layer is less than approximately 3 andgreater than approximately
 2. 17. A method for forming a touch sensor,the method comprising: providing a substrate comprising a first surface;forming a plurality of first electrodes comprising one or moreconductive materials on the first surface; and forming a dielectriclayer on the first electrodes and at least a portion of the firstsurface, the dielectric layer having a dielectric constant less than orequal to approximately
 3. 18. The method of claim 17, further comprisingattaching an electronic display panel to the substrate such that theelectronic display panel faces the dielectric layer, with an air gapdisposed between the dielectric layer and the electronic display panel.19. The method of claim 17, further comprising attaching an electronicdisplay panel to the substrate such that the dielectric layer is in atleast indirect contact with the electronic display panel.
 20. The methodof claim 17, wherein the dielectric constant of the dielectric layer isless than approximately 2 and greater than approximately 1.